For better understanding the principle of the present invention and for understanding the areas of application of the invented device, it would be advantageous to briefly familiarize yourself with anatomy of the eye. FIG. 1 is a cross-sectional view of a human eye. The definitions of the terms some of which is used in the description of the present patent application are given below.                The anterior chamber is the area bounded in front by the cornea and in back by the lens, and filled with aqueous.        The choroid, which carries blood vessels, is the inner coat between the sclera and the retina.        The ciliary body is an unseen part of the iris, and these together with the ora serrata form the uveal tract.        The conjunctiva is a clear membrane covering the white of the eye (sclera).        The cornea is a clear, transparent portion of the outer coat of the eyeball through which light passes to the lens.        Fundus is an inner wall of the eye.        The iris gives our eyes color and it functions like the aperture on a camera, enlarging in dim light and contracting in bright light. The aperture itself is known as the pupil.        The macula is a small area in the retina that provides our most central, acute vision.        The optic nerve conducts visual impulses to the brain from the retina.        The ora serrata and the ciliary body form the uveal tract, an unseen part of the iris.        The posterior chamber is the area behind the iris, but in front of the lens, that is filled with aqueous.        The pupil is the opening, or aperture, of the iris.        Retina is the innermost coat of the back of the eye, formed of light-sensitive nerve endings that carry the visual impulse to the optic nerve.        The retina may be compared to the film of a camera.        The sclera is the white of the eye.        The vitreous is a transparent, colorless mass of soft, gelatinous material filling the eyeball behind the lens.        
The techniques used for viewing the inner parts of the eye, such as retina and anterior chamber angle of the eye for evaluation, management, and classification of normal and abnormal structures is known as gonioscopy, and devices used for gonioscopy are known as gonioscopes. Observation of the anterior chamber and especially its angle areas, which are difficult or impossible to see with the use of some conventional optical means, is very important for diagnosis of eye diseases. For example, the classification of glaucoma relies heavily upon knowledge of the anterior segment anatomy, particularly that of the anterior chamber angle.
The anterior chamber of a human eye is commonly evaluated during slit lamp biomicroscopy, but the chamber angle is hidden from ordinary view because of total internal reflection of light rays emanating from the angle structures. In other words, without gonioscopy, the additional diagnostic clues of disease are forever hidden from ordinary view. It requires additional effort, skill and patient co-operation to view the normally concealed chamber angle by either indirect (angle structures viewed through a mirror) or direct (angle structures viewed directly) gonioscopic techniques. In other words, without gonioscopy, it is impossible to classify the glaucoma properly.
Heretofore, many gonioscopic devices have been known. The basic gonioscopic instrument used in the art is known as a Goldman “unversal” lens and mirrors or Roussel lens assembly. This gonioscope comprises an optical body with flat tapered sides having an entrance face which is flat or spherical, a spherical exit face which is applied to the cornea of the eye, a reflecting face and a compensating element, for example a plano-cylindrical lens. The Goldman gonioscope is a universal three-reflection lens assembly for biomicroscopic investigation and laser coagulation of the eye bottom and the front camera angle of the eye. With the help of lenses by Goldman in combination with a binocular microscope of a slit lamp a high quality image, a step-by-step observation of the eye bottom up to a tooth-like line, gonioscopy, detection of minute variation of eye structures under observation and spatial-depth localization of pathologic structures are provided.
Many other modifications of the Goldman gonioscope are known. Some of them are described below.
For example, U.S. Pat. No. 3,820,879 issued in 1974 to L. Frisen describes a contact glass device for biomicroscopic examination of the human eye comprising a lens body with a concave surface adapted for application upon the cornea of the eye to be examined with the optical axis of the lens coinciding with the optical axis of the eye and two light reflecting mirrors disposed at the side of the lens body opposite to the aforementioned concave surface so that the reflecting mirrors face each other on opposite sides of the optical axis of the lens. Furthermore, the mirrors are inclined at such angles relative to the optical axis of the lens body and to each other that it is possible to view the interior of an eye, on which the lens body is applied with its concave surface, in a non-reversible manner along a line of view which is reflected in the two mirrors and passes through the lens body. In one embodiment of the invention, one of the mirrors is pivoted relative to the lens body and allows observation of the anterior chamber from the central portion of the fundus of the eye radially outwardly to the boundary region of the fundus. Although the gonioscope of this type is efficient in its action, it cannot be easily sterilized because it comprises a complicated optical assembly.
U.S. Pat. No. 4,439,026 issued in 1984 to K. Wilms discloses an optical device with two reflecting surfaces which contains a contact glass with two reflecting surfaces for observing the chamber angle of a human eye in proximity of the iris, with a reflecting surface arranged laterally of the eye to be examined and a central reflecting surface to be located in the area of the common optical axis of the eye and of the axis of the contact glass. The path of observation rays is guided from the eye of the observer to the central reflecting surface and from the latter by way of the lateral reflecting surface into the interior of the eye whereby the lateral reflecting surface is so arranged to the common axis that its plane intersects the eye to be examined outside of the corneal area thereof and extends toward the eye to be examined up to a point to the rear of the center tangent of the eye abutment surface of the contact glass. In general, from the optical point of view the structure of this gonioscope is the same as in the previous patent and differs from it only by the fact that all reflecting angles are fixed and that the device has a monolithic structure more convenient for cleaning and sterilization. Various angles of observation may be achieved only by using a set of gonioscopes with different angles of reflecting mirrors.
U.S. Pat. No. 4,134,647 issued in 1979 to Ramos-Caldera discloses a contact lens for examining the interior of the eye. The inner walls of the eye, i.e., the fundus, are examined in panorama with an optical lens comprising a truncate paraboloidal mirror and a corneal contact objective lens. While held in contact with the cornea, the fundus is observed by projecting a light beam into the eye through the lens and viewing the interior eye with a microscope, e.g., a standard slit lamp instrument. Although this gonioscope allows seeing some hard-to-reach areas of the eye fundus, it has only one paraboloidal mirror, whereby the scope of observation is limited as compared to a conventional three-mirror Goldmal gonioscope.
U.S. Pat. No. 4,568,157 issued in 1986 to B. Kurwa describes a gonioscope that includes a truncated generally pyramidal body having four reflective sides, a concave smaller end face and an angled larger upper end face. The angled upper end face permits the use of a standard operating microscope since light produced by the microscope is reflected off-axis from the surface to minimize glare. The smaller end face has a curvature of approximately 43 diopters in order to seal mate with the human eye. The reflective sides of the lens enable the angle of the anterior chamber to be viewed by gonioscopy. The ratio of the height of lens to the width of its base is advantageously less than 2 and most advantageously approximately 1. The gonioscope of this type has a geometry modified for use only in combination with a microscope.
The idea of using curvilinear mirrors is further developed in U.S. Pat. No. 4,664,490 issued to P. Rol in 1987, which describes a monolithic gonioscopic lens of a conical shape for observation or treatment by irradiation of the eye, in particular the anterior chamber, outside of the optical axis of the eye. The device comprises a lens Goldman or Roussel lens, which, as has been described above, has flat tapered sides with an entrance face which is flat or spherical, a spherical exit face which is applied to the cornea of the eye, a reflecting face and a compensating element, for example a plano-cylindrical lens. The compensating element is fixed on the reflecting face and its function is to create an astigmatism effect, which is the reverse of that of the eye, for an incident light beam, which enters by way of the entrance face. It is understood that manufacture of aforementioned curvilinear compensation mirrors is a very complicated and expensive procedure. Furthermore, since curvatures on the anterior chambers vary from eye to eye, the approach used in the aforementioned patent may have a limited effect or requires a set of lenses.
U.S. Pat. No. 5,252,998 issued in 1993 to W. Reis et al. describes an instrument for the examination and/or treatment of the eye having an examination device designed for the examination of the fundus of the eye and having a contact eyeglass, which is provided with a lens which can be placed on the eye, the eye-facing surface of the lens being adapted to the curve of the cornea. The lens, which is placed on the eye, has no spherical power at least in the region of the optical axis. The device of the invention comprises a set of reflecting surfaces which are arranged at predetermined fixed angles in order to have an access to various hard-to-see areas of the eye fundus inaccessible with Goldman or Roussell lenses of other designs, e.g., such as one disclosed in U.S. Pat. No. 4,439,026 and U.S. Pat. No. 3,820,879. However, the gonioscope of this type requires the use of several mirrors located not on the side surfaces but rather in the central part of the gonioscope. As a result, the aperture of this optical device is reduced, and the light power is lost.
U.S. Pat. No. 5,359,372 issued in 1994 to H. Kida, et al. discloses a gonioscope for intraocular observation capable of optically recognizing an inner portion of an eyeball by contacting the contact lens on a surface of a cornea of an eye to be inspected through a light ray transmitted through an inner portion of the contact lens. The devices comprises: an optical path dividing member provided on an optical path for leading a light ray incident on the inner portion of the contact lens to the eye to be inspected for dividing a portion of the light ray on said optical path; and an index (image of an index mark) provided at a position approximately optically conjugate with a portion to be observed of the eye to be inspected on a divided optical path divided by the optical path dividing member. The portion to be observed and said index can be optically recognized by at least partially superposing a first image of the index on a second image of the portion to be observed. This device is specifically pointed out at the use of an index image and has limitations with regard to the areas of observation.
U.S. Pat. No. 5,501,217 issued in 1996 to S. Ishiguro, et al. discloses a gonioscope for intraocular observation including a lens body having a contact face to be brought into contact with cornea of an eyeball of a subject, and a lens support having a contact portion to be settled on sclera of the eyeball of the subject, the lens body and the lens support being assembled on each other by means of a slide mechanism so as to be movable relative to each other in the axial direction of the gonioscope, wherein the gonioscope body is capable of pressing the cornea of the eyeball of the subject by movement thereof in the axial direction of device relative to the lens support settled on the sclera of the eyeball of the subject. The contact lens of the present invention is of good operability and adapted to effectively prevent slipping of itself on the cornea of an eyeball. Optically, the gonioscope of this type is the same as conventional ones, but is more convenient in practice as it consists of two relatively moveable parts one of which is used as a support on the eye.
U.S. Pat. No. 5,537,164 issued in 1996 to A. Smith describes a retroilluminating indirect gonioprism comprising an optical prism, an oblique reflector and light baffle to reduce the intensity of light reflected from the gonioprism anterior surface back toward an observer, and an opaque surface to substantially prevent retinal burns when using the gonioprism with a directed energy beam. Retroillumination of anterior chamber structures is provided by fiber optics incorporated into the gonioprism housing, which direct light from an external source into the peripheral portion of the eye anterior chamber. This retroillumination increases the accuracy of identification of structural landmarks (e.g., the scleral spur) which are important in argon laser trabeculoplasty. A directed energy beam, as from a high-energy laser, may be directed through the gonioprism while an eye structure on which the beam is focused is observed through the gonioprism. First-surface reflection of a portion of the directed energy beam passes obliquely toward a light baffle and is substantially absorbed, while the transmitted portion of the beam is slightly laterally displaced and strikes the gonioprism anterior surface. The portion of the beam reflected from the gonioprism anterior surface back toward the observer again undergoes partial reflection oblique to the visual axis and slight lateral displacement before reaching the observer. Thus, the amount of light reflected from the gonioprism anterior surface back toward an observer is reduced. Substantial optical correction for astigmatism of oblique incidence and for assuring substantial parallelism between the observer's line-of-sight to the gonioprism and the gonioprism optical axis is preferably provided through appropriate configuration of at least one substantially convex surface which comprises at least a portion of the optical prism anterior surface. The gonioscope described in the above patent makes it possible to perform a laser operation on the eye simultaneously with observation of the operation sight through the same gonioscope. The device is complicated, expensive, and the use thereof for simple observation and diagnostic is unjustifiable.
Thus, it can be concluded that all gonioscopes, which are known to the applicant and some of which have been described above, have common drawbacks in that they have complicated fragile and delicate structures and are expensive in production. In most cases the known gonioscopes are specialized for specific operations and therefore have limited application. The reflective optical surfaces are open and can be easily damaged. In addition, the exposed mirror surfaces may be damaged during sterilization. In view of their high cost, all of them are not disposable.